In This Article Expand or collapse the "in this article" section Bystander Effect

  • Introduction
  • General Overviews
  • Textbooks
  • Journals
  • The Implicit Bystander Effect
  • The Positive Bystander Effect

Psychology Bystander Effect
David F. Urschler, Julia Fischer, Andreas Kastenmüller, Peter Fischer
  • LAST REVIEWED: 06 November 2018
  • LAST MODIFIED: 28 July 2015
  • DOI: 10.1093/obo/9780199828340-0172


The starting point for research on the bystander effect was the brutal rape-murder of Catherine “Kitty” Genovese in 1964. Kitty was stabbed to death in front of her apartment in Queens, New York, while thirty-eight people in her neighborhood witnessed, for approximately forty minutes (from the safety of their apartments), this cruel event without taking either active (e.g., trying to stop the perpetrator) or passive (e.g., calling the police) action. After that tragic event, Latané and Darley developed their famous process model of help-giving. In short, their model assumes that a bystander who witnesses a crisis situation has to progress through five sequential steps before he or she will intervene (for detailed information, see the Process Model of Help-Giving). Latané and Darley argued that the witnesses failed to intervene because there were too many of them. Therefore, the bystander effect is defined by an increased likelihood that individuals are less willing to intervene in critical situations the more other passive people are present. Compare the following situation with Kitty’s case. In 2001, a group of young right-wing skinheads chased a young Greek man in Munich, Germany. Subsequently, they caught him and brutally beat him. Again, several individuals witnessed this case of emergency, yet only one young man from Turkey decided to take action. He pulled the blood-stained victim aside and saved his life by risking his own. These examples give rise to the question: what factors influence bystanders to intervene in such situations or not to intervene? Since the 1960s many studies have been conducted to answer this question. One of the most common and influential factors that affects the willingness of bystanders to help is the number of individuals (the so-called bystanders) witnessing a case of emergency. Most classic studies have shown that the greater the number of bystanders, the less helping behavior is exhibited. However, some studies have revealed contradictory findings, especially those that are more recent. This article aims to clarify these contrasting results. Specifically, influential factors (i.e., the dangerousness of an emergency) that can reduce, or even reverse, typical bystander behavior are highlighted (for detailed information, see Influencing Factors).

General Overviews

Griggs and Proctor 2002 affirms that the bystander effect is one of most-cited effects in introductory psychology textbooks. Thus, almost any general introductory psychology textbook covers the bystander effect. The chapter on social psychology in Gerrig and Zimbardo 2008 provides a brief overview that gives the reader a first impression concerning the basic mechanisms behind the bystander effect. Almost all introductory textbooks in the field of social psychology cover the bystander effect. A good overview of the bystander effect (including historical and up-to-date findings) can be found in the chapter on prosocial behavior in Aronson, et al. 2012, a volume for undergraduate students in social psychology. The chapter on prosocial behavior in Fletcher and Clark 2003 provides a good introduction to the bystander effect.

  • Aronson, Elliot, Timothy D. Wilson, and Robin M. Akert. 2012. Social psychology. 8th ed. Harlow, UK: Pearson/Education.

    This text for undergraduate students covers the most important theories and phenomena in the field of social psychology. Includes a good presentation of the bystander effect.

  • Fletcher, Garth J. O., and Margaret S. Clark, eds. 2003. Interpersonal processes. Blackwell handbook of social psychology. Malden, MA: Blackwell.

    This edited volume provides an excellent overview of interpersonal processes. The chapter on prosocial behavior by Dovidio and Penner provides answers to the questions: When do people help? Why do people help? Who does help?

  • Gerrig, Richard J., and Philip G. Zimbardo. 2008. Psychology and life. 19th ed. Boston: Allyn & Bacon.

    This fundamental textbook provides a comprehensive overview of the most important psychological effects, including the bystander effect. All effects reviewed are connected with a student’s everyday life. Therefore, this book is highly recommended for those seeking an introductory text in psychology.

  • Griggs, Richard A., and Derrick L. Proctor. 2002. A citation analysis of who’s who in introductory textbooks. Teaching of Psychology 29.3: 203–206.

    DOI: 10.1207/S15328023TOP2903_04

    Griggs and Proctor’s article provides a comprehensive overview of the most-cited authors in introductory psychology textbooks. Latané is included among these authors, thus underscoring the centrality of the bystander effect.

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